<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="https://unpkg.com/vue"></script>
    <script >

        window.onload=function() {
            var data = {counter: 0}

            Vue.component('child', {
                // camelCase in JavaScript
                props: ['myMessage'],
                template: '<span>{{ myMessage }}</span>'

            })

            new Vue({
                el: '#example-2'
                ,data:{parentMsg:''}
            })
        }
    </script>
</head>
<body>
<div id="example-2">
    <input v-model="parentMsg">
    <br>
    <child v-bind:my-message="parentMsg"></child>
</div>
</body>
</html>